The present invention relates generally to a device and method for sensing the vibration or shock wave on the fuel return line of a fuel injection engine to obtain an electrical signal which may be usable for various purposes, such as in tachometer measurements.
A number of devices are known which provide a sensing mechanism for sensing the fuel applied through a fuel line to a fuel injection engine. One such system is shown in U.S. Pat. No. 3,327,526 issued to J. N. North wherein a sensing device is positioned around the fuel line and comprises a microswitch which is caused to open and close in response to the surge of fuel through the fuel line. Another such system for sensing the fuel injection to an engine is disclosed in U.S. Pat. No. 3,511,088 issued to P. R. Weaver. Another improved system for sensing the fuel injection to an engine is shown in U.S. Patent application Ser. No. 949,061 now U.S. Pat. No. 4,192,179 entitled Piezoelectric Transducer for Fuel Injection Engine, filed in the name of Edward Yelke, the inventor of the present invention.
In contrast to the prior art, the inventor has now found that a very useful electrical signal can be generated, such as for measuring rpm, by sensing or monitoring the fuel output or fuel by-pass system of a diesel engine. Also, the present invention provides an improved, yet simpler, transducer than those shown in the prior art.
Accordingly, it is a principal object of the present invention to provide a simple effective transducer to obtain an electrical signal to obtain rpm measurements.
The inventive transducer is widely useful since it operates with the fuel injection system of the associated diesel engine and a high pressure injection pump and injection lines are common to a vast majority of diesel engines.
The inventive transducer does not require a complex switching arrangement to correct for the large number of gear and pulley ratios that are available in current engines, and it also eliminates any switching requirements to compensate for varying numbers of cylinders in the engine.